The proposed project will determine structural elements for the enzyme responsible for nitrite reduction in dissimilatory denitrification. Proton nuclear magnetic resonance spectroscopy will be used to determine structure about the catalytic site heme groups, including the characterization of electronic states. Resonance raman spectroscopy will be used to investigate the vibrational states of the catalytic sites. The exact chemical structure of the prosthetic groups of the enzyme will be determined by purification of these from the intact enzyme and a structural determination through nuclear magnetic resonance, vibrational, optical, and mass spectroscopy. The interactions of oxides of nitrogen with whole cells will also be examined. The target enzyme system is representative of the general class of electron transport enzymes and proteins. Its study will promote the understanding on a fundamental level of this class which is responsible for energy production and respiration in all cells.